Q: What initially drew you to the APS?

Stuart: I’ve been using synchrotron radiation since 1982 and became a regular user of the APS in the early 2000s. My lab is located just an hour away, so I’ve often been one of the first users during the start of new operations cycles.

My first synchrotron experiments were at Daresbury Laboratory in the UK, using X-ray topography to visualize dislocations in high-purity niobium crystals. The ability to observe how a material changes before and after stress is a core theme that continues to guide my work.

That fundamental question has guided much of my work. When I moved to Northwestern in the late ’90s, APS’s proximity was a key draw. It enabled me to run synchrotron experiments on a flexible basis.

Q: Can you describe the research you’ve conducted at the APS? 

Stuart: My research focuses on how mineralized tissues respond to mechanical stress. Specifically, I study the interaction between collagen fibrils and bioapatitic nanocrystals in mammalian bone and in the mineralized cartilage of shark vertebral centra.

I divide beamtime strategically: half on reliable samples, and the rest split between refining earlier work and testing higher-risk ideas that might yield new insights.

Some of the techniques and contributions I’ve developed at the APS include:

• The first 3D characterization of sea urchin tooth substructures (2-BM, 2001)
• Use of WAXS and SAXS to study mineral and collagen response to in situ mechanical loading (1-ID, 2005)
• First microdiffraction tomographic reconstruction of internal specimen structure (1-ID, 2007)
• Identification of materials within an intact Egyptian mummy using WAXS (1-ID)
• Discovery of a foam-like architecture in the mineralized cartilage of shark vertebrae (2-BM)

Each of these efforts is tied together by a common goal: to better understand the microstructural mechanisms that allow biological materials to function and endure under stress.

Q: What role did the APS play in enabling or advancing your work? 

Stuart: The APS has been central to my work, both because of its technical capabilities and its people. Beamlines such as 1-ID enable internal strain and structural measurements with a level of precision difficult to achieve elsewhere.

Just as important are the long-term relationships I’ve built with beamline scientists over the past two decades. These collaborations have allowed us to refine methods together, respond quickly to challenges, and conduct experiments that push boundaries. The combination of reliable instrumentation and deep institutional knowledge at APS has made it a uniquely productive place for this kind of work.

Q: Has anything unexpected come out of your work with the APS, either in your results or in the process itself?

Stuart: One example is our work on shark vertebral cartilage at 2-BM. What appeared to be simple growth bands turned out to be part of a much more complex architecture; an interconnected mesh of microplates just five microns thick. This foam-like structure enables the tissue to compress significantly without damage, which may explain how sharks tolerate over 10 million cycles of loading throughout their lifetimes.

Another notable project involved scanning an intact Egyptian mummy. We were able to precisely target and characterize specific materials within the wrappings, using WAXS techniques at 1-ID. It was a technically demanding effort, but it demonstrated the sensitivity and versatility of the APS beamlines in a unique application.

Q: What impact has your research at the APS had on your work so far? What are you excited about exploring next?

Stuart: Several techniques I helped develop, such as in situ loading combined with tomography or diffraction, have been adopted by researchers worldwide. For example, an early mechanical testing setup I co-developed has since influenced commercial systems and synchrotron-based designs used for micro-CT experiments.

Looking ahead, I plan to explore how the upgraded APS might enable new types of high-energy diffraction and imaging experiments. I’m in early discussions with collaborators to explore how we might adapt our methods to leverage the benefits of upgraded beamlines, such as 20-ID.

I often pursue questions without fixed expectations. Failed experiments still reveal useful boundaries. That test, observe, and adapt mindset continues to shape my work at APS and beyond.